The present invention relates to the field of security devices. It is known to make a security device and to associate it with a document that is sensitive in terms of security, such as an identity document, in order to make said document secure. An effective security device is characterized in that it is difficult to produce or to reproduce, and difficult to modify in undetectable manner.
In known manner, an identity document includes an image associated with the holder of the identity document, such as an identity photograph. During an identity check, it is thus possible to compare an image comprising a photograph of the holder as present in the identity document, with an image acquisition performed on the bearer of the identity document in order to verify whether the acquired image does or does not correspond biometrically with the document image in order to determine whether the bearer is or is not the alleged holder.
Such a comparison is particularly probative when the image present on the identity document does indeed show the authorized holder. That is why it is appropriate to ensure that the image is indeed the authentic and original image as applied by an issuing authority, and that it has not been modified since it was issued.
In order to ensure that a counterfeiter can neither replace nor modify the image on the identity document, e.g. in order to attempt to reproduce the appearance of a bearer other than the holder, the image is advantageously associated with a security device. The security device is advantageously intimately linked with said image so that the security and authentication features of the security device also apply to the image.